It has long been known that boat operation can be improved by adding a pair of trim tabs to opposing sides of the stern of the boat as performance improvement devices. Such devices generally provide augmenting lift as effective hull bottom extensions to primarily level the boat fore and aft. Trim tabs, attached to the boat, aid in lifting the stern of the boat, thereby dropping the bow and consequently assisting the boat in getting to a planing orientation more quickly and with lower expenditure of fuel. Correctly designed and set trim tabs also stabilize the boat in pitch and roll.
The exact origin of trim tabs is unknown, however it is known that early trim tabs comprised pieces of wood or shingles attached to a hull bottom to extend aft of the transom of the boat. Modern hull extending trim tabs are usually attached to the transom. Such trim tabs most often consist of pairs of plates or planes of steel, aluminum or plastic rigidly mounted or hinged at or near the bottom edge of the transom. Some models are permanently fixed and are stationary relative to the transom. Other models are mechanically adjustable.
Adjustable models are usually more expensive than permanently fixed, stationary models. Such adjustable models generally comprise a flat plate hinged to the transom above the bottom of the boat and operated by a hydraulic cylinder or threaded screw actuator. Examples of adjustable devices are found in U.S. Pat. Nos. 3,062,178 and 2,928,365. A deflectable plastic trim tab is disclosed in U.S. Pat. No. 3,601,078.
Permanently fixed trim tabs generally comprise no moving parts. An example of a permanently fixed trim tab is disclosed in U.S. Pat. No. 4,323,027 which teaches a plastic trim tab made by vacuum forming. To provide a structure capable of withstanding forces associated with hydroplaning acceleration and high boat velocity, the plastic trim tab comprises a pair of side edges and a pair of more medially disposed semitubular gussets which are seen as raised and depressed structures, on the top and bottom surfaces, respectively, of the plastic trim tab. The semitubular surfaces provide strengthening gussets for the plastic trim tab and direct water in increased velocity streams toward a downwardly curved aft end portion thereof. Consistent with vacuum forming, an upwardly formed mounting plate provides a single mounting flange for the plastic trim tab.
Flexing of plastic trim tabs during use often results in premature fracture breaking mounting flanges away from water contacting surface components. In the cases of both the fixed and adjustable trim tabs, while the trim tabs generally rest in the water at a convenient level for use as a step, no trim tabs are currently known which comprise the strength or form for use in providing safe and efficacious entry and exit into and from the boat.